Internal combustion engine counterweight and cylinder construction



United AStates Patent INTERNAL COMBUSTION ENGINE COUNTER- WEIGHT Ann CYLINDER CONSTRUCTION Joseph D. Turlay, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application November 12, 1952, Serial No.

319,952. Divided and this application March 29, 1956, Serial No. 574,733

6 Claims. (Ci. i4-44) `This application is` a division of application S. 319,952, filed in the name of Joseph D. Turlay, November This invention relates to internal combustion engines and has particular relation to the construction of crankshaft counterweight means especially adaptable for use in engines where the pistons thereof extend below the cylinders as the pistons approach and recede from the i inner dead center positions of the pistons.

In the construction of internal combustion engines there are twoI .kinds ofk pistons which are sometimes used. These are called slipper pistons or trunk pistons depending upon .whether the bearing surfaces on the sides of the pistons are confined mostly to the opposite sides of the pistons or extend around the pistons ysubstantially 360. In the slipper pistons the bearing surfaces are confined to the opposite sides of the pistons and the intermediate side walls relieved or cut away so that the-parts of the pistons -below the pin bosses do not extend inwardly as far as do the parts of the pistons inwardly of the bearing surfaces. When such pistons are used it is possible to allow the bearing surface parts of the pistons to extend inwardly as the pistons approach and recede from inner dead center positions of the pistons without itnerfering with employment of counterweights of the `largest possible size. The counterweights will rotate within the relieved parts of the pistons below the pin bosses. However, when trunk pistons areemployed and these are allowed to extend below the lower ends of the` cylinderslas the pistons approach and recede from the inner dead centenpositions of the pistons, the sidesl of the pistons below the pin bosses may interfere with employing counterweights of the largest possible size. Since it is considered preferable in many instances to employ trunk pistons, it is proposed to devise counterweights having a peculiar exterior contour that will provide a relatively constant clearance between the counterweights and the pistons as the pistons move inwardly beyond the cylinders. Such contour permits the employment of counterweights having centers of mass farther l practices and of a suiciently small radius so that the from the axis of rotation of the crankshaft than otherwise would be possible.

In the drawing:

Figures 1, 2 and 3 are fragmentary cross sectional views of an internal combustion engine having pistons, cylinders and a crankshaft with counterweights, constructed according to the principles of the invention. Figures 1, 2 and 3 show different positions of the crankshaft counterweights and pistons in the engine.

Figure 4 is a fragmentary View of a V-type engine embodying the piston, cylinder, crankshaft and counterweight construction illustrated by Figures l, 2 and 3.

The internal combustion engine 10 embodying the invention may employ rows or banks of cylinders indicated at 11. The banks of cylinders may be constructed.

ICC

ders 22 adapted to receive trunk-type pistons indicated at 23. The pistons 23 are adapted to reciprocate in the cylinders 22 and to extend inwardly of the cylinders 22 as the pistons approach and recede from inner dead center positions `of the pistons in the cylinders. The pistons 23 have bearing surfaces extending substantially around the outer cylindrical surfaces of the pistons and the inner ends of the pistons terminate in planes substantially normal to the axes of the pistons. The pistons 23y have piston pins 26 by which the pistons are connected to the crankshaft 12 of the engine by connecting rods 24. The inner ends of thek connecting rods are attached in the usual manner to crankpins 27 of the crankshaft 12 which, in the present instances, are adapted to rotate in the directionindicated by the arrows thereon. The .crankshaft 12 may have any number of counterweights 53, the outer peripheral edges of which are indicated at 57.

In order to provide the greatest possible radius of gyration for the center of mass of counterweights 53 which are employed in counterbalancing the crankshaft 12 and to thereby decrease the amount of counterweighting re- `quired, it is proposed to constructthe counterweights 53 trates the rotation of the crankshaft 12 in the movement ofthe-piston 23 below the cylinder 22 and as the crankshaft approaches inner dead center. Figure 2 illustrates the position of these parts at inner dead center and Figure 3 illustrates the position of the same parts as the shaft moves beyond inner dead center. The circular arcs 59 shown in dot and dash lines illustrate what might be the contour ofthe outer edges 57 of the counterweights 53 were it' not for the movement of the pistons 23 below the lower extremities of the cylinders 22. The lowenextremities of the cylinders 22 at the front and rear sides of each of the cylinders 22 have arcuate cutaway or relief portions 58, which extend along circular arcs indicated in dot and dash lines at 56. The spaces between thearcs 56 and 59 illustrate the extentrto which the .counterweights 53 would clearrthe lower ends ofthe cylinders `22 if theouter peripheral edges of the counterweights 53 were constructed in such a way as to follow the contour of the arcs 59. However, it will be apparent from inspecting the drawing that pistons 23 do move below extremities of the cylinders 22. Therefore, the outer peripheral edges of the counterweights 53 cannot be constructed to follow the circular arcs 59. The circular arcs 61 illustrate what the contour of the outer eripheral edge of the counterweights would be if the counterweights 53 were constructed according to present peripheral edges of the counterweights would miss the lower edges of the pistons 22 when the pistons were at the inner extremity of the movement thereof. It will be apparent that all of the metal outside of the circular arcs 61 could not be utilized in making the counterweights 53 so that the counterweights would have to be made much wider and the engine crankshaft correspondingly longer in order to incorporate in the counterweights a sufficient amount of metal to counterbalance the crankshaft 12. Since the metal in the ycounterweights 53, which is disposed externally with respect to the circular arcs 61, has a center of mass which is much farther from the axis of rotation of the crankshaft than the center of mass of the counterweights 53, it will be apparent that the inertia effect of the rotation of the metal outside of the circular arc 61 is much greater than the inertia effect resulting from the rotation of any other part of the coun- 1.9 terweight 53 of similar weight. In order to gain this advantage from the metal in the counterweights 53 which appears as being outside the circular arcs indicated at 61, it is proposed to construct the peripheral edge 57 of the counterweights 53 on a line which includes the locus of all points equal in distance from the lower edges of the pistons 23 when the pistons Z3 move below the lower extremities of the cylinders 22. Under such circumstances as will be seen that the peripheral edges 57 of the counterweights will not only miss the lower ends of the cylinders 22 by a distance equal to the distance between the circular arcs 56 and 59 but between the opposite ends of the counterweights will miss the pistons when the pistons move below the lower extremities of the cylinders by. an amount equal to the distance between the linesindicated at 62. One of the lines indicated at 62 shows the position of the lower edge of the piston as the piston moves below the lower edge of the cylinder. The other of the lines indicated at 62 is tangent to the outer peripheral edges 57 of the counterweight 53 at the point nearest the lower edge of the piston. It will be apparent, therefore, that the counterweights 53 may be constructed in such a way that the center of mass of the counterweights have the greatest possible radius of gyration about the axis of rotation of the crankshaft 12, and at the same time will clear the lower extremity of the pistons by a uniform and sufficient distance.

I claim:

1. VVAn internal combustion'engine comprising a cylinder having a reciprocal piston therein and a crankshaft with a crank arm having a connecting rod connected to said piston, a counterweight formed on said crankshaft in opposed relation to said crank arm, said counterweight having a curved outer edge formed thereon, said curved outer edge being formed in part to clear said piston at the lower end of the travel of said piston by a uniform distance.

2. An engine comprising a row of cylinders having reciprocal pistons therein, a crankshaft mounted for operation along one end of said row of cylinders, said crankshaft being formed to provide crank arms for each of said cylinders, connecting rods connecting said crank arms to said pistons, said crankshaft also being formed to provide counterweights in opposed relation to said cylinders, said counterweights having outer edges approaching the inner ends of said pistons when said pistons approach inner dead centers during the operation of said engine, said outer edges of said counterweights being contoured to clear said piston ends by a uniform distance as said pistons approach and recede from inner dead centers during the operation of said engine.

3. An engine comprising a row of cylinders on each side of an intermediate plane extending through the axis of rotation of said engine, a crankshaft for said engine and mounted to rotate on said axis of said engine, said crankshaft having a single crank arm for operating a piston in each row of cylinders, a pair of connecting rods connected to each of said crank arms and to a piston in each row of said cylinders, counterweights formed on said crankshaft in opposed relation to certain of said crank arms, said counterweights having outer edges contoured at opposite ends of the edges thereof to clear the lower ends of said cylinders and between said ends of said edges to clear by a uniform distance the lower ends of said pistons when said pistons extend below the lower ends of said cylinders in approaching and receding from the inner dead center positions of said pistons.

4. An internal combustion engine comprising a cylinder having a piston therein and a crankshaft with a crank arm having a connecting rod connected to said piston, said crankshaft being connected by said connecting rod to said piston to move said piston inwardly beyond the inner end of said cylinder when said piston approaches and recedes from inner dead center position of said piston in said cylinder, a counterweight formed on said crankshaft in opposed relation to said crank arm, said crank arm being formed to provide an outer edge contoured to rotate inwardly of said piston when said piston approaches and recedes from said inner dead center position of said piston in said cylinder and to rotate inwardly of the inner end of said cylinder and without engaging said piston but clearing the inner end of said cylinder by a distance less than said piston moves inwardly of the inner end of said cylinder.

5. An internal combustion `engine as defined by claim 4 and in which the radii of curvature of the middle of said contoured edge is less than the lradii of curvature of the opposite ends of said contoured edge.

6. An internal combustion engine as defined by claim 4 and in which the radii of curvature of the middle of said contoured edge is less than the radii of curvature of one end of said contoured edge.

References Cited in the tile of this patent FOREIGN PATENTS 26,338 Great Britain Nov. 24, 1911 

